In a trapezium $ABCD$, $AD\parallel BC$, $AD=10\text{cm}$, $BC=5\text{cm}$, and $CD=10\text{cm}$. If $ABCD$ represents an isosceles right-height variant configuration where the non-parallel perpendicular height standard provides direct bounds, let's establish the calculation step using standard geometric parameters. Given structural norms for this platform textbook layout, evaluating the area directly via standard isosceles right drop properties gives $\text{Area}=75\text{sq.cm}$.

1. A
   150 sq.cm
2. B
   75 sq.cm
3. C
   500 sq.cm
4. D
   250 sq.cm